const clock = document.getElementById('clock-container');


Date.prototype.Format = function (fmt) {
  let hours = this.getHours()
  hours = hours % 12;
  hours = hours ? hours : 12;
  
  var o = {
      "M+": this.getMonth() + 1, //月份 
      "d+": this.getDate(), //日 
      "H+": hours, //小时 
      "m+": this.getMinutes(), //分 
      "s+": this.getSeconds(), //秒 
      "q+": Math.floor((this.getMonth() + 3) / 3), //季度 
      "S": this.getMilliseconds() //毫秒 
  };
  if (/(y+)/.test(fmt)) fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
  for (var k in o)
  if (new RegExp("(" + k + ")").test(fmt)) fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));
  return fmt;
}

setTimeout(() => {
  setInterval(() => {
    const now = new Date();
    clock.innerHTML = now.Format('HH:mm:ss');
  }, 1000)
}, 3000)

